Estimating in situ exposure in the presence of acoustic nonlinearity

Authors
Citation
Fa. Duck, Estimating in situ exposure in the presence of acoustic nonlinearity, J ULTR MED, 18(1), 1999, pp. 43-53
Citations number
26
Categorie Soggetti
Radiology ,Nuclear Medicine & Imaging
Journal title
JOURNAL OF ULTRASOUND IN MEDICINE
ISSN journal
02784297 → ACNP
Volume
18
Issue
1
Year of publication
1999
Pages
43 - 53
Database
ISI
SICI code
0278-4297(199901)18:1<43:EISEIT>2.0.ZU;2-R
Abstract
Evidence is presented for excess attenuation of pulsed ultrasound due to fi nite amplitude effects in water. Measurements on a modern scanner are used to demonstrate that linear derating can underestimate many exposure quantit ies, including all safety indices apart from the cranial thermal index. Mor e appropriate methods for estimating in situ exposure are reviewed. A prefe rred procedure that requires exposure measurements to be made in water unde r "small signal" conditions is selected. A spectral index is defined that i s proposed as an indicator of finite amplitude effects, where spectral inde x = 0.1 defines the threshold between nonlinear and quasi-linear conditions .